Erlkaf as an optional kafka client about broadway_kafka

[josevalim]

Hi @escobera! It may make sense but at the moment I am not sure if it is better as a separate library or by encapsulating the different behaviours in a client module. If you give it a try, please let us know how it goes. :)

[escobera]

Oh, I see what you mean.

I noticed some of the main modules (i.e. BroadwayKafka.KafkaClient and BroadwayKafka.Producer) depend explicitly on :brod types and/or behaviours. And since brod's and erlkaf's api differs violently this would be much harder to achieve then just creating another client module. I don't think I'm able to code this in a timely fashion, so I'll give it a try on my free time but will close this as not to polute the issue list.

Thanks @josevalim =)